The present invention is a method for GPS positioning in a weak signal environment. The method includes obtaining assistance data for a GPS signal from a satellite at a predetermined time, wherein the assistance data including predicted navigation data, Doppler shift and Doppler shift rate and the GPS signal being modulated by a carrier signal, a pseudorandom code and navigation data, estimating a predicted receiving time for the GPS signal reaching the GPS receiver, capturing the GPS signal, converting the GPS signal to an intermediate frequency signal, acquiring a code phase of the pseudorandom code from the intermediate frequency signal by using the assistance data and the predicted receiving time, and obtaining a position for the GPS receiver based on the predicted navigation data and the code phase of the pseudorandom code. To acquire the code phase of the pseudorandom code, the GPS receiver corrects a real time clock to one millisecond accuracy and process the intermediate frequency signal through coherent correlation of one second.